• Cattle nutrition and grazing behavior during short-duration-grazing periods on crested wheatgrass range

      Olson, K. C.; Rouse, G. B.; Malechek, J. C. (Society for Range Management, 1989-03-01)
      Daily changes in diet quality, ingestive behavior, and daily forage intake were investigated using crested wheatgrass [Agropyron desertorum (Fisch.) Schult. and A. cristatum (L.) Gaertn.] range in a 3-year study to provide an understanding of how the rapid defoliation that occurs under the high stocking density of short duration grazing (SDG) affects livestock nutrition. A 10-paddock short duration grazing cell was stocked with yearling Angus heifers. Grazing periods in paddocks varied from 1 to 4 days. Dietary quality was assessed daily within pre-selected paddocks by determining crude protein content and in vitro organic matter digestibility of extrusa samples collected from esophageally fistulated animals. Three variables of ingestive behavior were measured concurrently, including ingestion rate, biting rate, and grazing time. Daily forage intake was estimated by multiplying ingestion rate and grazing time. There were large daily changes in diet quality, ingestive behavior, and forage intake during the grazing period within particular SDG paddocks. Diet quality declined significantly during the 2 or 3 day grazing period in all 3 years. Although not as consistent throughout the study, ingestive behavioral responses changed significantly, indicating declines in forage intake during the grazing period on a particular paddock. Ingestive behavior was correlated with several characteristics of the sward that changed as it was defoliated. Ingestion rate decreased with herbage availability, apparently causing the animals to compensate by increasing biting rate or grazing time. Ingestion rate and biting rate decreased as nutritional quality of the sward declined, as indicated by decreased crude protein content and digestibility, and increased fiber content. Based on the system studied, grazing periods in SDG paddocks should be no more than 2 days to maintain high levels of livestock performance on crested wheatgrass range.
    • Comparing the economic value of forage on public lands for wildlife and livestock

      Loomis, J.; Donnelly, D.; Sorg-Swanson, C. (Society for Range Management, 1989-03-01)
      Deciding how to allocate forage among animals is a fundamentally important process in range management. The wisdom of these decisions can be enhanced by estimating the marginal value of forage needed by competing species. We present a method for obtaining such estimates and apply this method to generate net economic values of forage for elk and deer in Challis, Idaho. Specifically, a demand curve derived using a regional travel cost model is used to statistically estimate the marginal value of wildlife and forage. Comparisons of the value of forage to livestock and wildlife indicate equivalent values in the Challis, Idaho, area for these 2 uses.
    • Crested wheatgrass growth and replacement following fertilization, thinning, and neighbor plant removal

      Olson, B. E.; Richards, J. H. (Society for Range Management, 1989-03-01)
      The growth and annual replacement of crested wheatgrass (Agropyron desertorum (Fisch. ex Link) Schult.) tillers are affected by resource availability. Fertilization and grazing affect the resources available to crested wheatgrass plants directly, by increasing nutrient supply or by reducing photosynthetic area and root elongation, and indirectly, by changing the competitive status of neighboring plants. To determine the time and manner of crested wheatgrass response to alterations in resource availability, we assessed the growth, flowering, and replacement of tillers on plants treated as follows: tiller thinning, neighbor plant removal, combined thinning and neighbor plant removal, and nitrogen fertilization. These treatments were repeated on different sets of plants in early spring 1984 and 1985. Plant response was inferred from tiller heights, number of flowering culms, and new spring tiller production within the season of manipulation, and the number and heights of replacement tillers the following spring. Neighbor removal, and in 1 year fertilization, increased the size of tillers and stimulated the emergence of new spring tillers. Fertilization effects did not persist into the following year whereas neighbor removal increased annual tiller replacement at least two-fold on target plants. Tiller-tiller competition was not important in plants of crested wheatgrass because tiller growth and replacement on thinned plants did not differ from that of intact plants. This result occurred when thinned and intact plants were compared when both were growing with or without neighbors. Thinned plants replaced only the remaining tillers by the following spring. They did not regain their pretreatment status, presumably because of the encroachment of neighbors. These results indicate that thinned plants probably would lose their position in a plant community unless their neighbors are affected similarly.
    • Economic consequences of alternative stocking rate adjustment tactics: a simulation approach

      Riechers, R. K.; Conner, J. R.; Heitschmidt, R. K. (Society for Range Management, 1989-03-01)
      An economic analysis of alternative stocking rate adjustment tactics is performed using a simulation model which emulates the annual decision-making situation of a rancher. The model includes variation in livestock prices and annual forage production. The manager's decisions are based on the availability of forage at 4 decision points in the year, the expected growth between the current decision point and the next, and the expected portion of the forage that is to be harvested through grazing. Livestock are bought and sold to adjust the stocking rate to equal the expected available forage for grazing. Results are obtained for 3 different stocking tactics based on 4 levels of expected forage production and livestock utilization set at the May decision point. The results reflect the differences in net returns over variable costs and the differences in annual cow investment capital associated with each tactic. The results indicate that the tactics using a maximum stocking rate of 3.6 ha/au offer the most reasonable compromise between mean and variance of net returns. The tactic with no limit on stocking rate provides the possibility of obtaining higher average annual net returns than tactics with limited stocking rates, but the variation in annual returns is considerably greater and the annual cow investments costs are higher.
    • Experimental evaluation of the grazing optimization hypothesis

      Williamson, S. C.; Detling, J. K.; Dodd, J. L.; Dyer, M. I. (Society for Range Management, 1989-03-01)
      The herbivore grazing optimization hypothesis predicts an increase in aboveground net primary productivity (ANPP) at a moderate grazing intensity. The hypothesis was tested by grazing controlled densities (0 to 145 individuals/m2) of big-headed grasshoppers (Aulocara elliotti Thomas) for short time spans (7 to 13 days) on enclosed swards (0.7 m2) of blue grama [(Bouteloua gracilis) (Willd. ex H.B.K.) Lag. ex Griffiths]. ANPP of each of 257 experimental enclosures was estimated following regrowth by using a standing crop index (the product of mean total blade length per tiller and percent basal cover) after the grazing period and clipping after the regrowth period. ANPP was not significantly reduced by grazing in any of the 5 short-duration grazing experiments. In 2 of the 5 experiments, ANPP increased significantly with grazing. In 1 of the other 3 experiments there was evidence for the grazing optimization hypothesis.
    • Genetic variability of Mg, Ca, and K in crested wheatgrass

      Mayland, H. F.; Asay, K. H. (Society for Range Management, 1989-03-01)
      Increasing available Mg in crested wheatgrass (Agropyron spp.) could reduce the incidence of grass tetany (hypomagnesemia) in ruminants grazing this forage. Raising the Mg levels might be done through genetic processes if enough variation in ion concentration existed in the Agropyrons. The purpose of this study was to determine the genetic variation in Mg, Ca, and K concentrations in 2 crested wheatgrass populations. Parent plants were vegetatively propagated to provide 6 replicates each of 12 clones of crested wheatgrass (A. desertorum) and 16 F3 clones of colchicine-induced tetraploid A. cristatum X natural tetraploid A. desertorum. Each plant was selected on a basis of seedling and mature plant vigor, forage, and seed yield, leafiness, resistance to pests, and response to environmental stress. The 2 populations were grown in separate, space-planted nurseries at Logan, Utah. Herbage was harvested at the pre-boot and early flowering stage in each of 2 years. Magnesium and Ca were determined by atomic absorption and K by flame emission. A reduced tetany potential (RTP) index for each clone was calculated as the sum of normalized Mg and (Ca+Mg)/K values. Significant (P < 0.01) differences for all traits were detected among clones in each population. All traits, except K and RTP, were closely correlated. Broad-sense heritability values for most traits ranged from 0.61 to 0.84. Enough genotypic variation existed in both populations to warrant breeding lines with higher concentrations of Mg and larger RTP values. Such changes could reduce the incidence of grass tetany in livestock grazing crested wheatgrass.
    • Growth dynamics of fourwing saltbush as affected by different grazing management systems

      Price, D. L.; Donart, G. B.; Southward, G. M. (Society for Range Management, 1989-03-01)
      Individual leaders of fourwing saltbush were permanently marked and their growth responses monitored during a 3-year study in a shortduration grazing system, a 4-pasture rotation system, and in ungrazed exclosures. Primary and secondary leader growth and numbers of secondaries were responses of interest. Plants continuously browsed by cattle were usually maintained in a hedged form and produced relatively little growth. There was little difference in growth responses between plants in the 4-pasture rotation and the shortduration system when the shortduration rotation cycle was 32 days. However, when the rotation cycle was increased to 64 days, there was a substantial increase of growth for plants in the shortduration system. Plants protected from browsing for 1 year also responded with progressively less leader production as length of protection time increased. We suggest fourwing saltbush plants respond to a 60-day deferment at the beginning of the growing season.
    • Infiltration parameters for rangeland soils

      Rawls, W. J.; Brakensiek, D. L.; Savabi, M. R. (Society for Range Management, 1989-03-01)
      Important to the management of rangelands is knowledge of the water intake properties of their soils and the effect of soil surface and canopy cover. Using a data base of rangeland infiltration runs covering a wide range of soil and cover conditions, a procedure incorporating the effects of soil properties, soil surface cover, and vegetative canopy on the Green-Ampt hydraulic conductivity parameter was developed. Test results indicate that the estimated Green-Ampt parameters provided good predictions of the mean final infiltration rates and volumes for a variety of soil-cover situations.
    • Leafy spurge and the species composition of a mixed-grass prairie

      Belcher, J. W.; Wilson, S. D. (Society for Range Management, 1989-03-01)
      The relationship between leafy spurge (Euphorbia esula L.) and the species composition of mixed-grass prairie was examined on both a large scale, within a 200-km2 area, and on a local scale, within a single infestation. On the large scale, cover values of 8 of the 10 most common species varied significantly (P & 0.05) between native prairie and spurge-dominated vegetation. Cover values of all common native species were negatively correlated with cover of leafy spurge. Within a single infestation of leafy spurge, the frequency of 5 common native species decreased significantly with leafy spurge. Most native species were absent where leafy spurge was most abundant and species richness declined from 11 outside the infestation to 3 at the center. Ninety-five percent of leafy spurge infestations within a 374-ha area were associated with anthropogenic disturbances (vehicle tracks, road construction and fireguards) which removed native plant cover and exposed mineral soil. These observations corroborate experimental studies which show that leafy spurge establishes more readily in disturbed soil and indicate that the result of such disturbances is the replacement of native species with leafy spurge.
    • Observation on cattle liveweight changes and fecal indices in Sudan

      Hasham, I. M.; Fadlalla, B. (Society for Range Management, 1989-03-01)
      Changes in liveweight of sedentary and migratory herds of cattle in south Kordofan Province, Sudan, were determined monthly. Feces of these animals were analyzed for N and ADF during the same period. Both the sedentary and the migratory herds gained liveweights during periods August to September and November to February and lost liveweight during October and from March to July. Changes in liveweights were more highly related to fecal ADF concentrations (r = -0.60, P<0.002) than to fecal N concentrations (r = -0.085, P<0.305).
    • Observations on biomass dynamics of a crested wheatgrass and native shortgrass ecosystem in southern Wyoming

      Redente, E. F.; Biondini, M. E.; Moore, J. C. (Society for Range Management, 1989-03-01)
      Above- and belowground net primary production (ANPP and BNPP) were compared between a 30-year-old crested wheatgrass site and an adjacent native shortgrass prairie. ANPP was estimated using successive harvests in May, June, July, and October 1985. BNPP was estimated using soil cores to a depth of 100 cm at the same time that aboveground harvests were made. ANPP was significantly greater in the crested wheatgrass site compared to the native site, but belowground and total net primary production were not different. The native shortgrass system, however, had greater live root biomass early in the growing season. The crested wheatgrass system had a high accumulation of aboveground dead material at the start of the growing season, which was followed by a significant decline in June and an increase in July and October. The native shortgrass system, however, had significantly lower accumulations of aboveground dead material. Approximately 92% of the fixed carbon in the native site was allocated belowground, while crested wheatgrass allocated about 85% of its fixed carbon belowground.
    • Pinyon-juniper chaining and seeding for big game in central Utah

      Skousen, J. G.; Davis, J. N.; Brotherson, J. D. (Society for Range Management, 1989-03-01)
      Vegetation and soils were evaluated on 5 different-aged, mechanically treated and seeded pinyon-juniper sites and compared to adjacent untreated areas. Plant cover was significantly changed after treatment: trees were reduced from 26 to 6% total ground cover; shrubs were increased from 2 to 8% ground cover; and herbaceous plants increased from 2 to 13% ground cover. Annuals and perennial forbs were 75% of the total plant cover on the 2-year-old site, perennial grasses and shrubs dominated the plant cover (52 to 83%) on three, 14- to 20-year-old sites, while shrubs and trees combined for 94% of the plant cover on the 24-year-old site. Two Agropyron grass species showed good establishment and persistence after seeding. Seeded forbs contributed about 5% of the total plant cover on the 2-year-old treated site and they declined on older treated sites. Seeding of shrubs was only successful on sites where the shrub species was already present in the understory naturally. Seeding of nonnative shrub seed did not produce stands. Even though tree cover was reduced after treatment, total tree density was not. Shrub density increased from an average of 800 plants/ha on untreated areas to 2,750 plants/ha on treated areas. Juniper mortality during mechanical treatment varied from 60 to 91% and was related to the percentage of trees estimated to be 60+ years old (r = 0.97) and with the number of trees greater than 5 cm in stem diameter (r = 0.71) on the adjacent untreated sites. Big game pellet group counts were not different between untreated and treated sites, suggesting that big game make use of these treated areas because of increased forage and browse and in spite of reduced security cover.
    • President's Address: Is it time for a change?

      Laycock, William A. (Society for Range Management, 1989-03-01)
    • Seeded wheatgrass yield and nutritive quality on New Mexico big sagebrush range

      Holechek, J. L.; Estell, R. E.; Kuykendall, C. B.; Valdez, R.; Cardenas, M.; Nunez-Hernandez, G. (Society for Range Management, 1989-03-01)
      Establishment, yield, and nutritional quality of 'Nordan' crested wheatgrass (Agropyron desertorum [Fischer ex Link] Schultes), 'Fairway' crested wheatgrass (Agropyron cristatum [L.] Gaertner), 'Arriba' western wheatgrass (Pascopyrum smithii [Rydb.] A. Love), 'Luna' pubescent wheatgrass (Thinopyrum intermedium subsp. barbulatum [Schur.] Barkw. and D.R. Dewey), and 'Largo' tall wheatgrass (T. ponticum [Pod] Barkw. and D.R. Dewey) were evaluated on big sagebrush range (Artemisia tridentata Nutt. tridentata) in northcentral New Mexico during a 5-year study. All the above wheatgrasses showed high initial densities and long-term persistence. Wheatgrass yields across years and seasons during the last 2 years of study averaged 760 kg/ha compared to forage yields of 355 kg/ha on surrounding ungrazed native rangeland. There were no differences (P > .05) among wheatgrasses in standing crop of current year's growth during spring, summer, or fall. Crude protein concentrations did not differ (P > .05) among wheatgrasses with seasonal advance. However, all the wheatgrasses showed a consistent decline in nutritional quality from spring to summer to fall. All the wheatgrasses we studied will provide high-quality, spring (mid-April to mid-June) forage for livestock. During summer, use of native range is advantageous because it contains a high component of warm season grasses and forbs. Interseeding shrubs in wheatgrass seedings could reduce protein supplementation costs in winter.
    • Silicon in C-3 grasses: effects on forage quality and sheep preference

      Shewmaker, G. E.; Mayland, H. F.; Rosenau, R. C.; Asay, K. H. (Society for Range Management, 1989-03-01)
      Silicon in forage reduces dry matter digestibility and may reduce grazing preference. Two studies were conducted with the following objectives: (1) to evaluate a method of determining grazing preference, and (2) to characterize the distribution and solubility of silicon in 31 accessions of C-3 grasses and relate these traits to grazing preference and estimated forage digestibility. Forage samples were clipped at the beginning of each 7 to 10-day grazing period corresponding to 6 phenological stages of the Agropyron sp. Samples were washed and analyzed for acid detergent fiber (ADF), neutral detergent fiber (NDF), and silicon in ADF and NDF residues. Leaf silicon concentrations increased from the vegetative to seed-ripe stage. Genera were aligned into 3 groups based on the increase in leaf silicon concentration with advancing phenological age. Silicon concentrations in leaves of Agropyron, Pseudoroegneria, and Thinopyrum increased at nearly twice the rate of those in Critesion, Hordeum, Leymus and Psathyrostachys. Elymus leaves contained higher concentrations of silicon at the vegetative stage than the other groups, but the accumulation rate was intermediate. About 32% of total leaf silicon remained in NDF and 76% in ADF residues at the vegetative stage. These insoluble portions of silicon increased with aging. Preference was positively related to estimated dry matter digestibility at boot and anthesis, but was not related to fiber or silicon measurements. Leaf harshness was negatively related to preference at seed-ripe stage. Further progress in characterizing the role of silicon in C-3 forage grasses should be possible by studying a representative species from each group.
    • Some effects of a rotational grazing treatment on cattle preference for plant communities

      Walker, J. W.; Heitschmidt, R. K.; Dowhower, S. L. (Society for Range Management, 1989-03-01)
      Rotational grazing is commonly assumed to improve livestock distribution compared to continuous grazing, but little evidence supports this contention. Research was conducted on the effects of rotational grazing (RG) compared to continuous grazing (CG) on the preference of cattle for plant communities. Different livestock densities in the RG treatments were created by varying the size of paddocks in a 465-ha, 16-paddock, cell designed RG treatment stocked at a rate of 3.6 ha/cow/yr. Paddock sizes of 30 and 10-ha were used to simulate RG with 14 (RG-14) and 42-paddocks (RG-42), respectively. The CG treatment consisted of a 248-ha pasture stocked at 5.9 ha/cow/yr. Data consisted of hourly daylight observations of cattle location and activity during 8 seasonal trials lasting 6-15 days. These data were expressed as a percent of the time cattle were observed in each of 4 plant communities and the area surrounding permanent water. Relative electivity (RE), a preference index, and a selectivity index (SI) that measures departures from random distribution were calculated from these data. Relative electivity (i.e., preference) for plant communities was not affected by grazing treatment. However, cattle were less selective for plant communities as livestock density decreased from the RG-42 to the CG treatment. In the RG-14 treatment, the cattle were either unaffected or less selective on the last day than on the first day in a paddock. We hypothesize that grazing systems influence cattle preference for plant communities by affecting the availability of forage biomass per unit land area rather than by their effect on grazing pressure.